Reaction force type disk brake

ABSTRACT

Since slide-pin support portions and first braking-torque support portions are independent of each other in the body of a bracket included in a reaction force type disk brake, even if the first braking-torque support portions have deflected more or less by supporting the braking torque of a first friction pad, the deflections are not transmitted to the slide-pin support portions. Accordingly, no twists take place between slide pins and the slide-pin support portions. Besides, in the bracket, the support points of the respective slide pins are arranged in a region defined between second and third straight lines, so that even when the braking torque of a second friction pad has acted on the slide-pin support points through second braking-torque support portions as well as the slide pins on account of the shortened distances between the slide-pin support points and bracket fixation points, turning moments which arise about the fixation points are small. Accordingly, a brake caliper is permitted to slide smoothly, and the durability of the bracket for supporting the brake caliper can be enhanced.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the present invention is reaction force type disk brakes,of a type which is mainly used for vehicles such as automobiles, andmore particularly, improvements in a reaction force type disk brakecomprising a first and a second friction pad facing opposite faces of abrake disk, respectively; a brake caliper provided with a first and asecond clamping arm for clamping both the friction pads; opposite endsof the brake caliper in a circumferential direction of the brake diskbeing supported by a pair of slide-pin support portions of a fixedbracket through slide pins outside an outer periphery of the brake diskfor sliding movements in a direction of a rotational axis of the brakedisk; an urging member provided on the first clamping arm and having acenter of urging at a central position of the first friction pad in thecircumferential direction of the brake disk for urging the firstfriction pad to the brake disk; a pair of first braking-torque supportportions mounted on the bracket for supporting a braking torque of thefirst friction pad; and a pair of second braking-torque support portionsmounted on the brake caliper for supporting a brake torque of the secondfriction pad; wherein a pair at which fixing points of the bracket isfixed to a stationary member located at opposite sides of a firststraight line which passes the center of urging and a center of rotationof the brake disk, the fixing points being disposed on a second straightline which crosses the first straight line at a location closer to thecenter of rotation with respect to the center of urging.

2. Description of the Prior Art

Heretofore, the disk brake of the type described above, is already knownfrom, e.g., Japanese Patent Application Laid-open No. 22660/1977.

In such a disk brake, a single block protruded from the body of thebracket is commonly used by the first braking-torque support portionsfor supporting the braking torque of the first friction pad and theslide-pin support portions for supporting the slide pin.

In addition, the slide-pin support points, at which the slide pins aresupported are arranged closer to the outer periphery of the brake diskthan to a third straight line which is parallel to the second straightline and which passes the urging center.

In the above disk brake, when braking, since the braking torqueeffecting on the first friction pad is supported by the firstbraking-torque support portions, the first braking-torque supportportions deflect in some degree If the single block is commonly used asin the conventional disk brake under such circumstances, the deflectionof the first braking-torque support portions are directly transmitted tothe slide-pin support portion. And as a result, a twist may arisebetween the slide pin and the slide-pin support portion, therebydeteriorating the smooth slide movement of the brake caliper which isundesirable.

Moreover, if the slide-pin support point is arranged as described above,a distance between the slide-pin support point and the fixing pointbecomes long. Therefore, when the braking torque effecting on the secondfriction pad has acted on the slide-pin support point through the secondbraking-torque support portion as well as the slide pin, a turningmoment of relatively large magnitude is generated about the fixingpoint. This is undesirable for improving the durability of the bracket.

SUMMARY OF THE INVENTION

In view of the above, the object of the present invention is to providea reaction force type disk brake in which the deflection of thebraking-torque support portion is prevented from being transmitted to aslide-pin support portion and in which a turning moment about the fixingpoint can be made small.

To achieve the above object, according to the present invention, thereis provided a reaction force type disk brake comprising a first and asecond friction pad facing opposite faces of a brake disk, respectively;a brake caliper provided with a first and a second clamping arm forclamping both the friction pads; opposite ends of the brake caliper in acircumferential direction of the brake disk being supported by a pair ofslide-pin support portions of a fixed bracket through slide pins outsidean outer periphery of the brake disk for sliding movements in adirection of a rotational axis of the brake disk; an urging memberprovided on the first clamping arm and having a center of urging at acentral position of the first friction pad in the circumferentialdirection of the brake disk for urging the first friction pad to thebrake disk; a pair of first braking-torque support portions mounted onthe bracket for supporting a braking torque of the first friction pad;and a pair of second braking-torque support portions mounted on thebrake caliper for supporting a brake torque of the second friction pad;wherein a pair at which fixing points of the bracket is fixed to astationary member are located on opposite sides of a first straight linewhich passes the center of urging and a center of rotation of the brakedisk, the fixing points being disposed on a second straight line whichcrosses the first straight line at a position closer to the center ofrotation with respect to the center of urging. and wherein the slide-pinsupport portions and the first braking-torque support portions areindependently mounted on a body of the bracket, and slide-pin supportpoints of both the slide-pin support portions are arranged in a regiondefined between the second straight line and a third straight line whichpasses through the center of urging in parallel with the second straightline.

According to this arrangement, since the first braking-torque supportportion and the slide-pin support portion are independently provided inthe body of the bracket, the deflection of the first braking-torquesupport portion is not transmitted to the slide-pin support portion.Thus, a twist between the slide pin and the slide-pin support portiondue to a braking torque can be prevented from occurring, and the brakecaliper is permitted to smoothly slide at all times.

Moreover, by disposing both the slide-pin support points are arranged inthe specific region as described above, turning moments which ariseabout the respective fixing points during supporting the braking torquecan be made small. Thus, the durability of the bracket can be improved.

The above and other objects, features and advantages of the presentinvention will become apparent from the following description ofpreferred embodiments taken with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1 to 9 illustrate a first embodiment of the present invention, inwhich FIG. 1 is a plan view of a reaction force type disk brake, FIG. 2is a view taken along an arrow 2 in FIG. 1, FIG. 3 is a view taken alongan arrow 3 in FIG. 1, FIG. 4 is a sectional view taken along a line 4--4in FIG. 2, FIG. 5 is a perspective view of a bracket, FIG. 6 is asectional view taken along a line 6--6 in FIG. 2, FIG. 7 is a sectionalview taken along a line 7--7 in FIG. 1, FIG. 8 is a sectional view takenalong a line 8--8 in FIG. 2, and FIG. 9 is a perspective view showingthe relationship between a vehicle body and the disk brake;

FIG. 10 illustrates a second embodiment and is a view corresponding toFIG. 3; and

FIG. 11 illustrates a modification of the second embodiment and is aview corresponding to FIG. 3.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The first embodiment of the present invention will be described withreference to FIGS. 1 to 9.

The drawings illustrate a reaction force type disk brake D for anautomobile. Referring to FIGS. 1 to 4, a brake disk 1 is rotatable witha wheel in a direction of an arrow a during forward travel of theautomobile and in a direction of an arrow b during backward travel,respectively. First and second friction pads 3₁, 3₂ are disposed in anopposed relation to opposite side surfaces of the brake disk 1. Thesepads 3₁, 3₂ are clamped by first and second clamping arms 5₁, 5₂ of abrake caliper 4. Opposite ends of the brake caliper 4 located in acircumferential direction of the brake disk 1 are supported by a bracket6 so as to slide along an axis of rotation c of the brake disk 1 at anouter periphery thereof. The bracket 6 is fixed to a knuckle 7 which isa stationary member.

As shown in FIGS. 5 and 7, the body 6a of the bracket 6 is formed in aplate-like shape of a narrow width so as to face one side surface of thebrake disk 1. A pair of first braking-torque support portions 8 areraised on opposite ends of the body 6a in an opposed relation to eachother, while a pair of cylindrical slide-pin support portions 9 arecontinuously provided at opposite ends of the body 6a with axes of thesupport portions 9 being parallel to the axis of rotation c of the brakedisk 1. Thus, the first braking-torque support portions 8 and theslide-pin support portions 9 are provided on the body 6a independentlyof each other.

As clearly shown in FIGS. 1 and 6, each of the first and second clampingarms 5₁, 5₂ has a pair of lugs 10 at opposite ends of each arm in thecircumferential direction of the brake disk 1. Slide pins 11 areprovided to extend between the two pairs of opposed lugs 10 of both thearms 5₁, 5₂ and are slidably fitted in the slide-pin support portions 9of the bracket 6, respectively. Each slide pin 11 is provided at a baseend thereof with an external thread portion 11a which is threaded in atapped hole 12 formed in each the lug 10 on the side of the firstclamping arm 5₁, while a tip end of each slide pin 11 is fitted in a pinhole 13 formed in each the lug 10 on the side of the second clamping arm5₂.

A portion of each slide pin 11 between the lug 10 and the slide-pinsupport portion 9 is covered with expansion dust-proof boot 15.

The brake caliper 4 is comprised of a block 17₁ having the firstclamping arm 5₁, and a block 17₂ having the second clamping arm 5₂. Apair of opposing protrusions of both the blocks 17₁, 17₂ are connected,thereby to form a pair of bridge portions 16 which connect the end partsof both the clamping arms 5₁, 5₂ in the circumferential direction of thebrake disk 1. Both the blocks 17₁, 17₂ are secured by two pairs ofconnecting bolts 18, 19 at the bridge portions 16.

A window 21 is defined by the first and second clamping arms 5₁, 5₂ andboth the bridge portions 16. Both the inner ends of the window 21 in thecircumferential direction of the brake disk 1 are formed with steps 22which extend along the axis of rotation c.

Each of the friction pads 3₁, 3₂ comprises a back plate 23, and a lining24 attached to this back plate. As clearly shown in FIG. 7, hookportions 23a formed at opposite ends of each back plate 23 in thecircumferential direction of the brake disk 1 are suspended on the steps22 through retainers 25 for sliding movements along the axis of rotationc.

As clearly shown in FIG. 8, at the central part of the window 21 in thecircumferential direction of the brake disk 1, a pin hole 26 is formedthrough the first and second clamping arms 5₁, 5₂ so as to extend alongthe axis of rotation c. A hanger pin 27 is removably inserted into thepin holes 26 between the arms 5₁ and 5₂.

The back plates 23 of both the friction pads 3₁, 3₂, are provided attheir central portions in the circumferential direction of the brakedisk 1 with projections 23b. The hanger pin 27 is inserted through boththrough holes 28 formed in the projections 23b. Thus, both the frictionpads 3₁, 3₂ are suspended by the hanger pin 27.

The hanger pin 27 is prevented from slipping out from the secondclamping arm 5₂ by engaging a stopper 29 provided on the base end ofthis hanger pin with an edge of the pin hole 26. On the other hand, thehanger pin 27 is prevented from slipping out from the first clamping arm5₁ in such a way that a hook-shaped slip-out preventing plate 31 isengaged with the tip end of the hanger pin at the portion projected fromthe outer side surface of the first clamping arm 5₁. The plate 31 issecured to the first clamping arm 5₁ by a screw 32. The tip end of thescrew 32 abuts against the hanger pin 27 so as to urge this hanger pinagainst the inner peripheral surface of the pin hole 26. Thus, thehanger pin 27 is prevented from loosening or rattling in the axial andradial directions thereof.

As clearly shown in FIGS. 1 and 7, a pad spring 33 is retained to thehanger pin 27, and the opposite ends of the pad spring 33 resilientlyurge the hook portions 23a of the first and second friction pads 3₁, 3₂against the steps 22. Thus, both the friction pads 3₁, 3₂ are preventedfrom rattling.

As clearly shown in FIG. 7, the opposite end faces of the back plate 23of the first friction pad 3₁ in the circumferential direction of thebrake disk 1 abut against the first braking-torque support portions 8,respectively.

Likewise, as shown in FIG. 7, a pair of second braking-torque supportportions 34 for supporting the braking torque of the second friction pad3₂ are protrusively provided at the base ends of both the constituentparts of the bridge portion 16 in the block 17₂ on the side of thesecond clamping arm 5₂. And the opposite end faces of the back plate 23of the second friction pad 3₂ in the circumferential direction of thebrake disk 1 abut against both the second braking-torque supportportions 34, respectively.

In the above construction, replacement of the friction pads 3₁, 3₂ areconducted through the window 21.

As clearly shown in FIGS. 2 and 4, a pair of cylinders 35 whose openingsare directed to the first friction pad 3₁ are formed along thecircumferential direction of the brake disk 1 in the part of the firstclamping arm 5₁ between both the connecting bolts 18. One of thecylinders 35 is communicated with a known master cylinder through apressure oil introducing port 36, and interiors of both the cylinders 35are communicated with each other through a communicating hole 37.

A piston 38 as an urging member, which urges the first friction pad 3₁against the brake disk 1, is slidably fitted in each cylinder 35.

As shown in FIG. 7, the urging center O₁ of both the pistons 38 existsat the central position of the first friction pad 3₁ in thecircumferential direction of the brake disk 1, that is, at thebisectional point of a straight line L₃ connecting the axes of both thepistons 38, in the illustrated embodiment.

A pair at which fixing points of the bracket 6 is fixed to the knuckle7, i.e., a pair of centers O₃ of fixing bolt inserting holes 39 in theillustrated embodiment are disposed on one face side of the brake disk 1on a first straight line L₁ which passes the urging center O₁ and acenter of rotation O₂ of the brake disk 1. The centers O₃ are set on asecond straight line L₂ crossing the first straight line L₁ (at rightangles in the illustrated embodiment) at a position closer to the centerO₂ with respect to the center O₁. In addition, the centers O₃ arerespectively located on opposite sides of the first straight line L₁.

The slide-pin support points of both the slide-pin support portions 9,that is, the centers O₄ of pin inserting holes 40 in the illustratedembodiment, are respectively arranged in a region defined between thesecond straight line L₂ and a third straight line L₃ which passesthrough the urging center O₁ in parallel with this second straight lineL₂.

As clearly shown in FIG. 3, three reinforcing ribs 41 which aresubstantially straight are formed on the outer side surface of thesecond clamping arm 5₂ and substantially in parallel with one another soas to extend near to opposite ends of this clamping arm 5₂ in thecircumferential direction of the brake disk 1.

Next, the operation of this embodiment will be described.

During forward travel of the automobile, when a brake pedal or the likeis operated pressure oil is supplied from the master cylinder (notshown) into both the cylinders 35 through the pressure oil introducingport 36. Both the pistons 38 advances by the hydraulic pressure to urgethe first friction pad 3₁. Consequently, the friction pad 3₁ moves whilesliding on the step 22 of the brake caliper 4 and the hanger pin 27 andis urged against one face of the brake disk 1. Then, by a reactionattendant upon the urging, the brake caliper 4 slides in the directionopposite to advance of both the pistons 38 through the slide pins 11.The second friction pad 3₂ is urged against the other face of the brakedisk 1 by the second clamping arm 5₂. Thus, braking is applied to thebrake disk 1.

During such braking, the braking torque of the first friction pad 3₁ issupported by the first braking-torque support portions 8 of the bracket6, while the braking torque of the second friction pad 3₂ is supportedby the second braking-torque support portions 34 of the brake caliper 4.

In this case, when the first braking-torque support portions 8 supportsthe braking torque of the first friction pad 3₁, the portions 8 deflectmore or less. However, since the first braking-torque support portions 8and the slide-pin support portions 9 are independent of each other, suchdeflections are not transmitted to the slide-pin support portions 9.Thus, the twists between the slide pins 11 and the slide-pin supportportions 9 attributed to the braking torque are prevented fromoccurring.

Besides, if the relationship of arrangement between the slide-pinsupport points O₄ and the fixing points O₃ of the bracket 6 is specifiedas stated above, the distance between the points O₄ and O₃ is shortened.Therefore, even when the braking torque of the second friction pad 3₂has acted on the slide-pin support points O₄ through the secondbraking-torque support portions 34 as well as the slide pins 11, turningmoments which is generated about the fixing points O₃ are relativelysmall. Thus, the durability of the bracket 6 can be enhanced.

FIG. 9 shows the relationship between the disk brake D and a vehiclebody B. The brake caliper 4 is disposed so that the window 21 isdirected to a front direction of the vehicle and the second clamping arm5₂ is located on the side of a wheel W, and the bracket 6 is fixed tothe knuckle 7. The brake disk 1 is secured to a hub 42 for mounting thewheel W.

If the brake caliper 4 is disposed in this manner, airstream isintroduced into the brake caliper 4 through the window 21, and thereinforcing ribs 41 function also as cooling fins. Therefore, thefriction pads 3₁, 3₂ and the brake caliper 4 can be efficiently cooled.

FIG. 10 illustrates the second embodiment of the present invention. Thisembodiment has an arrangement similarly to that of the first embodimentexcept that, in a second arch clamping arm 5₂ which extends along thearc shape of a brake disk 1, a pair of lugs 10 located at opposite endsof this arm 5₂ in the circumferential direction of the brake disk 1 areconnected by a tie bar 44.

If both the lugs 10 are connected by the tie bar 44 as described above,when a braking torque is supported on the side of the second clampingarm 5₂, it is possible to restrain the displacement of one of the lugs10 by the tie bar 44. Thus, the twists between slide pins 11 andslide-pin support portions 9 can be prevented from occurring, therebycontributing to the smooth slide movement of a brake caliper 4.

In addition, FIG. 11 illustrates a modification of the secondembodiment. A connection portion 45 for connecting a tie bar 44 with asecond clamping arm 5₂ is provided at the intermediate portion of thetie bar 44, thereby enhancing the strength of the tie bar 44.

What is claimed is:
 1. A reaction force type disk brake comprising afirst and a second friction pad facing opposite faces of a brake disk,respectively; a brake caliper provided with a first and a secondclamping arm for clamping both the friction pads; opposite ends of thebrake caliper in a circumferential direction of the brake disk beingsupported by a pair of slide-pin support portions of a fixed bracketthrough slide pins outside an outer periphery of the brake disk forsliding movements in a direction of a rotational axis of the brake disk;an urging member provided on the first clamping arm and having a centerof urging at a central position of the first friction pad in thecircumferential direction of the brake disk for urging the firstfriction pad to the brake disk; a pair of first braking-torque supportportions mounted on the bracket for supporting a braking torque of thefirst friction pad; and a pair of second braking-torque support portionsmounted on the brake caliper for supporting a brake torque of the secondfriction pad; whereina pair of fixing points at which the bracket isfixed to a stationary member are located on the opposite sides of afirst straight line which passes the center of urging and a center ofrotation of the brake disk, the fixing points being disposed on a secondstraight line which crosses the first straight line at a location closerto the center of rotation with respect to the center of urging, andwherein a slide-pin support portions and the first braking-torquesupport portions are formed in a body of the bracket in a bifurcatedmanner from the fixing points, and slide-pin support points of both theslide-pin support portions are arranged in a region defined between thesecond straight line and a third straight line which passes through thecenter of urging in parallel with the second straight line.
 2. Areaction force type disk brake according to claim 1, wherein a pair oflugs provided at opposite end portions of said second clamping arm inthe circumferential direction of said brake disk for supporting saidslide pins are connected integrally by a tie bar.
 3. A reaction forcetype disk brake according to claim 1, wherein the first braking torquesupport portions are located in a region defined between the second andthird straight lines.